The long-range goal of the proposed research is to elucidate the mechanisms which regulate the biosynthesis of the fatty acids which provide the fatty acyl chains of the major lipid classes (structural and storage) in mammalian cells. The immediate objective is to focus on the enzyme acetyl CoA carboxylase (ACC), which plays a critical role in the biosynthesis of these fatty acids, and to elucidate the molecular mechanisms underlying the regulation of the activity and content of this key enzyme in mammalian tissues. We will attempt to resolve hepatic ACC into functional subunits analogous to those previously isolated from Escherichia coli. The isolated subunits, including the biotin carboxyl carrier protein component, will be characterized with respect to their catalytic and regulatory functions. Rapid changes in the catalytic efficiency of ACC in response to allosteric effectors and possibly phosphorylation/dephosphorylation of the enzyme will be studied in mouse fibroblast (L cells) in tissue culture by combined enzymatic, isotopic and immunological techniques. In addition, the role of the turnover of the prosthetic group of ACC will be studied in these cells. Longterm adaptive changes in content of ACC in response to nutritional, hormonal and genetic alterations of fatty acid metabolism will be studied in tisues of normal and genetically obese mice, and the proteolytic machinery responsible for the normal turnover of ACC will be characterized. The role of ACC in the regulation of lipogenesis in extrahepatic tissues, especially lung, will be investigated. Mammalian lung ACC will be isolated and characterized, and its role in the regulation of fatty acid and pulmonary surfactant synthesis during fetal lung development will be evaluated, especially in regard to its role in infant respiratory distress syndrome. Agents (i.e., tryptophan catabolites) which induce symptoms of pulmonary edema and emphysema in cattle are also potential inhibitors of lung ACC (our preliminary observations), and therefore the involvement of ACC in the pathophysiology of these diseases will be explored.